'^'"D?c"'i8?2!'™"}        Examination  of  Balsam  of  Peru.  613 
acetone  or  alcohol  indicates  an  adulteration  with  benzoin ;  but  if  a 
white  powder  insoluble  in  acetone  or  alcohol  be  left,  it  shows  an  adul- 
teration with  storax.  This  powder  may  then  be  dissolved  in  chloro- 
form and  left  to  crystallize. 
Scheme  for  the  Qualitative  Examination  of  Balsam  of  Peru. 
(1)  .  The  specific  gravity  should  be  determined.  It  should  never 
fall  below  1-135. 
(2)  .  Upon  shaking  1  gram  of  balsam  three  or  four  times  with  sev- 
eral grams  of  petroleum  spirit,  not  more  than  '05  gram  should 
be  taken  np,  so  as  to  be  left  behind  upon  evaporation.  Otherwise  an 
admixture  of  castor  oil  or  copaiba  balsam  would  be  probable.  The 
latter  would  be  recognizable  by  the  odor  of  the  essential  oil. 
(3)  .  Dissolve  1  gram  of  balsam  in  several  grams  of  carbon  bisul- 
phide and  estimate  the  undissolved  portion,  dried  at  140°C.  This 
should  not  amount  to  more  than  0T6  gram,  otherwise  an  admixture  of 
benzoin  is  probable. 
(4)  a.  Mix  1  gram  of  balsam  with  1  to  1*2  gram  of  concentrated 
sulphuric  acid.  If  frothing  and  a  smell  of  burning  sulphur  be 
observed,  an  admixture  of  copaiba  balsam  is  probable.  (Confirm  by 
tests  2  and  5.) 
b.  After  the  mixture  has  cooled  w^ash  it  first  with  hot  and  then  with 
cold  water.  The  residue  should  be  at  first  plastic  and  afterwards  hard 
and  brittle.  A  smeary  character  indicates  an  admixture  with  castor 
oil.    (Confirm  by  test  2.) 
c.  Dry  the  washed  resinous  mass  superficially  with  blotting  paper, 
and  dissolve  it  in  several  grams  of  ether.  It  should  dissolve  com- 
pletely ;  if  an  insoluble  residue  be  left  it  indicates  an  admixture  of 
benzoin  or  storax.  Treat  this  insoluble  residue  with  strong  alcohol, 
or  preferably  witli  acetone.  If  it  dissolves  (completely,  the  adulterant 
is  benzoin,  in  cases  where  carbon  bisulphide  leaves  more  than  16  per 
rent,  of  the  balsam  undissolved  (test  3).  If  after  treatment  with 
alcohol  (or  acetone)  there  remains  a  white  powder,  easily  soluble  in 
chloroform,  and  separating  in  microscopic  crystals  upon  evaporation  of 
the  solvent,  storax  is  present.    (Confirm  by  test  5.) 
(5)  .  Dis^:olve  1  gram  of  balsam  in  3  grams  of  amuionia  solution, 
S})ecific  gravity  •960.  No  gelatinization  of  the  mixture  should  take  place 
or  appearance  of  gelatinous  fragments  swimming  in  ihe  ethereal  layer; 
otherwise  storax  is  present.   (Confirm  by  test  4.)   The  mixture  should 
